Apparatus of clamping semiconductor devices using sliding finger supports

ABSTRACT

An apparatus for supporting lead fingers during a wire bonding process and method of preventing the bonding apparatus and clamping assembly from applying force against the die. The present invention includes the use of a movable arm with a portion that is positionable under a portion of the lead fingers of a lead frame during the wire bonding process to provide increased stability of the lead fingers and prevent the bonding apparatus and clamping assembly from applying force against the die. The present invention also provides for the transfer of heat from the heat block directly to the lead fingers during the wire bonding process. The present invention includes the use of a clamp for stabilizing lead fingers during the wire bonding process.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of application Ser. No.09/840,289, filed Apr. 23, 2001, pending; which is a continuation ofapplication Ser. No. 09/358,248, filed Jul. 21, 1999, now U.S. Pat. No.6,227,431, issued May 8, 2001; which is a divisional of application Ser.No. 09/244,702, filed Feb. 4, 1999, now U.S. Pat. No. 6,299,057, issuedOct. 9, 2001; which is a continuation of application Ser. No.08/709,639, filed Sep. 9, 1996, now U.S. Pat. No. 5,890,644, issued Apr.6, 1999; which is a continuation-in-part of application Ser. No.08/631,143, filed Jun. 17, 1996, now U.S. Pat. No. 5,673,845, issuedOct. 7, 1997; application Ser. No. 08/597,616, filed Feb. 6, 1996, nowU.S. Pat. No. 5,647,528, issued Jul. 15, 1997; and application Ser. No.08/592,058, filed Jan. 26, 1996, now U.S. Pat. No. 5,954,842, issuedSep. 21, 1999.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention is related to forming wire bonds betweenthe contact pads on semiconductor devices and individual lead framefingers of a lead frame.

[0004] More specifically, the present invention is related to theapparatus and method of supporting the lead fingers of a lead frameduring a wire bonding process using a support arm with a lead supportportion that is positionable between the lead fingers and the die priorto the bonding process to help substantially stabilize the lead fingersduring the bonding process.

[0005] 2. State of the Art

[0006] Well known types of semiconductor devices are connected to leadframes and subsequently encapsulated in plastic for use in a widevariety of applications. Typically, the lead frame is formed from asingle continuous sheet of metal by metal stamping operations. In aconventional lead frame, the lead frame includes an outer supportingframe, a central semiconductor chip supporting pad and a plurality oflead fingers, each lead finger having, in turn, a bonding portionthereof near the central chip supporting pad. Ultimately, the outersupporting frame of the lead frame is removed after the wire bondsbetween the contact pads of the semiconductor chip device and the leadfingers are made and the semiconductor device and a portion of the leadframe have been encapsulated.

[0007] In the assembly of semiconductor devices utilizing suchconventional lead frames, a semiconductor die is secured to the centralsupporting pad (such as by a solder or epoxy die-attach, although adouble-sided adhesive tape-type attach has also been suggested in theart) and then the entire lead frame, with the semiconductor die thereon,is placed into a wire bonding apparatus including a clamp assembly forholding the lead frame and die assembly, and clamping the lead fingersfor bonding.

[0008] In contrast to a conventional lead frame, U.S. Pat. No. 4,862,245issued Aug. 29, 1989 to Pashby et al. illustrates a so-called “leadsover chip” arrangement (“LOC”) on the semiconductor die. A plurality oflead fingers of the lead frame extends over the active surface of asemiconductor die toward a line of bond pads thereon wherein bond wiresmake the electrical connection between the lead fingers and the bondpads. An alpha barrier such as a polyamide tape (for example, Kapton™tape) is adhered between the semiconductor die and the lead fingers.This configuration, which eliminates the use of thepreviously-referenced central die attach pad, may assist in limiting theingress of corrosive environment contaminants after encapsulation of thesemiconductor device, achieve a larger portion of the lead finger pathlength encapsulated in the packaging material, and reduce electricalresistance caused by the length of the bond wires (i.e. the longer thebond wire, the higher the resistance) and potential wire sweep problemsin the encapsulation of the semiconductor device aggravated by long wireloops.

[0009] In a standard wire bonding process, the bond wires are attached,one at a time, from each bond pad on the semiconductor device to acorresponding lead finger. The bond wires are generally attached throughone of three industry-standard wire bonding techniques: ultrasonicbonding—using a combination of pressure and ultrasonic vibration burststo form a metallurgical cold weld; thermocompression bonding—using acombination of pressure and elevated temperature to form a weld; andthermosonic bonding—using a combination of pressure, elevatedtemperature, and ultrasonic vibration bursts.

[0010] To form a good bond during the wire bonding processing, it ispreferable to perform the bonding at an elevated and somewhat stabletemperature. Therefore, as noted above, the lead frame assemblyincluding the attached semiconductor die is generally placed on a heaterblock. The semiconductor die is then clamped (via the lead frame) to theheater block by a clamping assembly. With a conventional lead frame, thelead fingers are clamped directly against the underlying heater block.Whereas, in a LOC lead frame, the lead fingers are biased between theclamp and the active surface of the semiconductor die heater block.Thus, in a LOC lead frame arrangement, the clamping assembly and bondingapparatus apply pressure against the die thereby causing possibledamage. In addition, heating of the lead fingers in a LOC lead frame forwire bonding must be done through heating the die as opposed to directlyheating the lead fingers by the heater block in a conventional leadframe.

[0011] Therefore, in a LOC lead frame configuration it would beadvantageous to develop an apparatus to prevent the clamping assemblyand bonding apparatus from applying force against the die. In addition,it would be advantageous to develop an apparatus for transferring heatdirectly from the heat block to the lead fingers.

[0012] In a LOC structure, the Kapton™ tape comprising the alpha barrieror dielectric between the semiconductor and the lead fingers becomessoft at the elevated temperature. The softening of the tapes allows thelead fingers and/or semiconductor die to move in response to ultrasonicenergy or pressure (force) exerted by the wire bonding head (capillary).As a result, the mechanical integrity of the wire bond to the leadfingers is diminished. Furthermore, a “bouncing” motion is imparted tothe lead fingers by the wire bonding head movement, which motion may beexacerbated by the heat softened tape. This bouncing motion can alsoresult in poor wire bonds which subsequently fail.

[0013] Thus, die fabricators are somewhat compelled to select the dieattach compound (or other means) and alpha barrier tape based on thethermal stability of the materials rather than on the basis of the mosteffective material for a given application.

[0014] Therefore, it would be advantageous to develop an apparatus thatwould replace the alpha barrier tape while stabilizing the semiconductordie and the lead fingers during the wire bonding process.

[0015] Typical apparatus and methods for clamping the lead frame duringthe wire bonding process or for clamping and advancing the lead frameare illustrated in U.S. Pat. No. 4,765,531, 5,082,165, 5,238,174,5,264,002, 5,307,978, 5,322,207, and 5,372,972. However, such apparatusand methods do not address the problem of supporting the lead fingersduring the wire bonding process or preventing the application of forceon the die.

[0016] Such prior art apparatus and methods have been directed atadvancing and orienting the lead frame but have not attempted to solvethe problems of forming reliable wire bonds between the contact pads ofsemiconductor devices and lead fingers of lead frames.

[0017] There have been other attempts to overcome the problem of thebouncing motion imparted to the lead fingers by the wire bonding headmovement. For example, for bonding LOC structures, rigid clamping plateshaving bond site windows therein have been reconfigured so that the bondsite window is reduced in size and the downwardly-extending lip orperiphery contacts the lead fingers extending over the die and clampsthe lead fingers directly thereto. However, the rigid clamp has beenfound to be too rigid and unyielding for use with a LOC configuration,and may possibly damage the die. Moreover, the use of a rigid clamp addsto the force exerted against the die and does nothing to prevent theapplication of force by the bonding apparatus.

[0018] The present invention is directed to an improved wire bondingapparatus and method for forming such wire bonds.

BRIEF SUMMARY OF THE INVENTION

[0019] The present invention is related to the apparatus and method ofsupporting lead fingers during a wire bonding process. The presentinvention includes the use of a movable arm having a lead supportportion for positioning under the lead fingers of a lead frame and/orbetween the die and the lead fingers during the bonding process toprovide increased stability of the individual lead finger for improvedbonding and to prevent the bonding apparatus and clamping assembly fromapplying force to the die. The present invention also provides for heatto be directly transferred from the heat block to the lead fingersduring the wire bonding process.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0020] The present invention will be better understood when thedescription of the invention is taken in conjunction with the drawingswherein:

[0021]FIG. 1 is a side view of the present invention used in the wirebonding of a semiconductor device arrangement having a conventional leadframe;

[0022]FIG. 2 is a cross-sectional view taken along A-A of the presentinvention as depicted in FIG. 1 and further shows one method of dynamicattachment;

[0023]FIG. 3 is a cross-sectional view taken along A-A of the presentinvention as depicted in FIG. 1 and further shows another method ofdynamic attachment;

[0024]FIG. 4 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a conventional lead frame;

[0025]FIG. 5 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a conventional lead frame;

[0026]FIG. 6 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a conventional lead frame;

[0027]FIG. 7 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a conventional lead frame;

[0028]FIG. 8 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a conventional lead frame;

[0029]FIG. 9 is a side view of the present invention used in the wirebonding of a semiconductor device arrangement having a LOC lead framewithout the leads adhered to the semiconductor device;

[0030]FIG. 10 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a LOC lead frame without the leads adhered to the semiconductordevice;

[0031]FIG. 11 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a LOC lead frame without the leads adhered to the semiconductordevice;

[0032]FIG. 12 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a LOC lead frame without the leads adhered to the semiconductordevice;

[0033]FIG. 13 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving an LOC lead frame without the leads adhered to the semiconductordevice;

[0034]FIG. 14 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a LOC lead frame without the leads adhered to the semiconductordevice;

[0035]FIG. 15 is a side view of the present invention used in the wirebonding of a semiconductor device arrangement having a LOC lead framewith the leads adhered to the semiconductor device;

[0036]FIG. 16 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a LOC lead frame with the leads adhered to the semiconductordevice;

[0037]FIG. 17 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a LOC lead frame with the leads adhered to the semiconductordevice;

[0038]FIG. 18 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a LOC lead frame with the leads adhered to the semiconductordevice;

[0039]FIG. 19 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a LOC lead frame with the leads adhered to the semiconductordevice;

[0040]FIG. 20 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a LOC lead frame with the leads adhered to the semiconductordevice;

[0041]FIG. 21 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a two piece lead frame with the leads adhered to thesemiconductor device;

[0042]FIG. 22 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a two piece lead frame with the leads adhered to thesemiconductor device;

[0043]FIG. 23 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a two piece lead frame with the leads adhered to thesemiconductor device;

[0044]FIG. 24 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a two piece lead frame with the leads adhered to thesemiconductor device;

[0045]FIG. 25 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a two piece lead frame with the leads adhered to thesemiconductor device;

[0046]FIG. 26 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a two piece lead frame with the leads adhered to thesemiconductor device;

[0047]FIG. 27 is a side view of an alternative embodiment of the presentinvention used in the wire bonding of a semiconductor device arrangementhaving a hybrid lead frame with leads on differing levels;

[0048]FIG. 28 is a view of the alternative embodiment of the presentinvention illustrated in drawing FIG. 27 with the alternative embodimentrotated ninety degrees (90°) to illustrate the lead support for the leadfingers of the hybrid lead frame;

[0049]FIG. 29 comprises a flow chart of an exemplary process sequencefor plastic package molding of a semiconductor device wire bonded to alead frame using the lead support of the present invention;

[0050]FIG. 30 is a side schematic view of a typical transfer moldillustrating a premolding encapsulant position;

[0051]FIG. 31 is a side schematic view of a typical transfer moldillustrating a postmolding encapsulant position;

[0052]FIG. 32 illustrates a top schematic view of one side of a transfermold of FIGS. 28 and 29 depicting encapsulant flow and venting of theprimary mold runner and the mold cavities wherein the die assemblies arecontained;

[0053]FIG. 33 depicts a first encapsulant flow scenario for a moldcavity during molding a lead frame and semiconductor manufactured usingthe present invention of a lead bonding support;

[0054]FIG. 34 depicts a second encapsulant flow scenario for a moldcavity during molding a lead frame and semiconductor manufactured usingthe present invention of a lead bonding support; and

[0055]FIG. 35 depicts a third encapsulant flow scenario for a moldcavity during molding a lead frame and semiconductor manufactured usingthe present invention of a lead bonding support.

DETAILED DESCRIPTION OF THE INVENTION

[0056] Referring to drawing FIG. 1, a semiconductor device (die) 10 isshown being supported by the paddle 12 of a conventional lead frame. Aheat block 20 is used to heat the paddle 12 and die 10 during the wirebonding process. As shown, a suitable wire 16 has one end thereof 17bonded to a bond pad of the die 10. The wire 16 may be of any suitabletype for connection and bonding purposes, such as gold, gold alloy,aluminum, aluminum alloy, etc. The other end 18 of the wire 16 is shownbeing bonded to the end 15 of a lead finger 14 of the lead frame by asuitable bonding apparatus 26. The bonding apparatus 26 may be of anysuitable type well known in the bonding area, such as a taillessthermosonic or ultrasonic capillary type bonding apparatus whichdispenses wire during the bonding process. If desired, in the wirebonding operation, further shown in contact with lead finger 14 is aportion of a conventional clamp 22 used to clamp portions of the leadframe during such bonding operations. The conventional clamp 22 may beof any well known suitable type, such as those described hereinbefore,and is generic in shape. Further shown in drawing FIG. 1 is a movableand/or adjustable arm 24 having a lead support portion 25 attached to oran integral part of the movable and/or adjustable arm 24. The movableand/or adjustable arm 24 is dynamically attached to the heat block 20 sothat the lead support portion 25 can be positioned between the die 10and the lead fingers 14. The movable and/or adjustable arm 24 and leadsupport portion 25 thus allow for any desired size semiconductor device10 to be wire bonded without a change to the heat block 20. In addition,movable and/or adjustable arm 24 having lead support portion 25 conductsheat from the heat block 20 to the lead fingers 14.

[0057] During the wire bonding process, it is desirable for the heatblock to be heated to substantially 230 degrees Centigrade. Although theheat block may be any suitable temperature during the bonding operation,the heat block 20 temperature should not exceed 300 degrees Centigradeto prevent thermal damage to the die 10. It is further preferred thatthe bond of the end 18 of the wire 16 made to the end 15 of the leadfinger 14 of a conventional lead frame be made at a temperature ofsubstantially 190 degrees Centigrade for bonding effectiveness. It isalso preferred that the bonding apparatus exert a bonding force ofsubstantially 50 to 100 grams when bonding the end 18 of the wire 16 tothe end 15 of lead finger 14 for effective bond formation of the wire 16to lead finger 14.

[0058] The movement of the movable and/or adjustable arm 24 may beeffectuated by various means 28. Such means are well known in themanufacturing area and may include an air cylinder, a solenoid, a magnetsystem, a motor, sprockets, a cable and pulley system, a lead screw, acam arrangement, etc.

[0059] The movable and/or adjustable arm 24 is dynamically attached tothe heat block 20 so that as the heat block moves into position duringthe wire bonding process. The movable and/or adjustable arm 24 havinglead support portion 25 moves into position under the lead fingers 14.Still referring to FIG. 1, movable and/or adjustable arm 24 is shown astraveling against the heat block 20 such that the direction of travel issubstantially parallel with respect to the lower surface 19 of the leadfingers 14 of a conventional lead frame.

[0060] Referring to drawing FIG. 2, one method for dynamically attachingmovable and/or adjustable arm 24 to heat block 20 is by atongue-and-groove type connection. A tongue 30 shaped in the form of adove tail is formed in the heat block 20. A mating groove 32 is formedin movable and/or adjustable arm 24 so that the tongue 30 may slidewithin the groove. Thus, movable and/or adjustable arm 24 is allowed toslide with respect to heat block 20 while maintaining contact with theheat block for efficient heat transfer. Alternatively, a tongue could beformed in the movable and/or adjustable arm and the groove could beformed in the heat block. Other tongue-and-groove connections may beeffectuated by forming different shaped tongue and grooves. For example,a square shaped tongue may be formed in heat block 20 and a matinggroove formed in movable and/or adjustable arm 24. To reduce friction,linear bearings 42 may be used as well as low friction pads 44 orlubricants.

[0061] Referring to drawing FIG. 3, another method for dynamicallyattaching movable and/or adjustable arm 24 to the heat block 20 is byhaving movable and/or adjustable arm 24 travel in a track 48 that isformed in heat block 20. Thus, movable and/or adjustable arm 24 isallowed to slide with respect to heat block 20 while maintaining contactwith the heat block for efficient heat transfer. Again, movement may befacilitated by the use of linear bearings 42 or low friction pads 44 orlubricants. Other methods for dynamically attaching the movable and/oradjustable arm 24 to the heat block 20 are tracks, a track-and-carriagesystem, a hinge, a cam arrangement, etc.

[0062] Referring to drawing FIG. 4, movable and/or adjustable arm 24 maybe attached to heat block 20 such that the direction of travel withrespect to lower surface 19 of lead fingers 14 is angular or arcuate. Aradius 54 may be formed in heat block 20 and movable and/or adjustablearm 24 such that the direction of travel of lead support portion 25 andmovable and/or adjustable arm 24 is arcuate with respect to lowersurface 19 of the lead fingers 14 of a conventional lead frame as thelead support portion is positioned prior to wire bonding.

[0063] Referring to drawing FIG. 5, the surface of the heat block 20 andmovable and/or adjustable arm 24 may also be angled 56 with respect tolower surface 19 of the lead fingers 14 such that the direction oftravel of lead support portion 25 and movable and/or adjustable arm 24is angular with respect to lower surface 19 of lead fingers 14 as thelead support portion 25 of movable and/or adjustable arm 24 ispositioned prior to the wire bonding process.

[0064] The movement of the movable and/or adjustable arm 24 and the heatblock 20 may be integrated so that as the heat block moves into positionit causes the movable and/or adjustable arm to move into position. InFIG. 5, a notch 50 is shown formed in movable and/or adjustable arm 24and extends into a slot 52 formed in a stationary member (not shown).Thus, as the heat block 20 moves upward to contact the die 10, the heatblock pushes against the movable and/or adjustable arm 24 which isforced to travel upward and inward by the notch 50 traveling in the slot52.

[0065] Referring to drawing FIG. 6, a dual clamp assembly is shown inconjunction with the movable and/or adjustable arms 24 in order tofurther stabilize the lead fingers during the wire bonding process. Theconventional clamp 22 acts as a primary clamp and includes a bond sitewindow 60. The bond site window 60 is sized to allow access for abonding apparatus 26 to a plurality of bond pads of semiconductor die 10and to a plurality of lead fingers 14 of a conventional lead frame.

[0066] The bond site window 60 includes a secondary clamp 62. Thesecondary clamp 62 is mounted to a resilient plate 64 with a first setscrew or bolt 66. The proximal end of each resilient plate 64 isattached to the conventional clamp 22 with a second set screw or bolt68. It is, of course, understood that secondary clamp 62 can be attachedto the conventional clamp 22 in any number of known configurations,including forming the secondary clamp 62 with an integral resilientportion which is secured to the conventional clamp 22 or forming (forexample, as by machining) the secondary clamp 62 as an integrated,resilient appendage of the conventional clamp 22. It is, of course, alsounderstood that any number of secondary clamps 62 can be used,consistent with the need for adequate clearances for wire bonding.

[0067] When a semiconductor die 10 and a lead frame strip including leadfingers 14 of a conventional lead frame, is aligned with the bond sitewindow 60 in the conventional clamp 22 and pressure is exerted on thelead frame, the contact end 63 of the secondary clamp 62 contacts themovable and/or adjustable arm 24 through lead fingers 14 extending fromthe lead frame over the active die surface. The secondary clamp 62 doesnot damage the semiconductor die 10 under the secondary clamp contactend 63 because of the resilient nature of the secondary clamp 62 andbecause of movable and/or adjustable arm 24 positioned between thesemiconductor die 10 and the secondary clamp 62.

[0068] The semiconductor die 10 has a conventional lead framearrangement wherein the lead fingers 14 extend adjacent the upper(active) semiconductor die 10. The bond site window contact lip 65contacts the lead fingers 14 around the periphery of the semiconductordie 10. The secondary clamp 62 extends toward the center of thesemiconductor die 10. A plurality of wires 16 is then attached betweenthe bond pads of the semiconductor die 10 and the lead fingers 14.

[0069] The contact end 63 of the secondary clamp 62 in its unbiasedstate preferably extends slightly below the bond site window contact lip65 of the bond site window 60 of the conventional clamp 22. Thesecondary clamp 62 may be formed from a substantially rigid,non-deformable material such as metal, high-temperature plastic, fibercomposites, or the like. A preferred material for the secondary clamp 62is 440C stainless steel.

[0070] Referring to drawing FIG. 7, an independently actuated lead clampis shown in conjunction with the movable and/or adjustable arms 24 inorder to further stabilize the lead fingers during the wire bondingprocess. Independently actuated lead clamp 70 may be used in place of orin addition to the conventional clamp 22 to maintain the lead finger 14in position during the bonding process. The conventional clamp 22 helpsinsure that the lead finger is in contact with the movable and/oradjustable arm 24 during the bonding process and helps minimize anydeflection of the end 15 of the lead finger 14 so that the bondingapparatus 26 accurately and precisely contacts the end 15 to provide thedesired wire bond. The action of independent actuated lead clamp 70 and,if desired, the additional use of conventional clamp 22, providesimproved clamping of a lead finger 14 during the wire bonding process aswell as insures that the lead finger 14 of a conventional lead frame isin intimate contact with the movable and/or adjustable arm 24 foreffectiveness.

[0071] Independent actuated lead clamp 70 may be of any suitable shapefor use in independently clamping the lead finger 14, in place of theuse of conventional clamp 22, such as square, semicircular, rectangular,arcuate, etc. Also, the independent actuated lead clamp 70 may beresiliently mounted through the use of a shoulder 72 thereon abutting aspring 74 to control the amount of the force exerted on any lead finger14 during the wire bonding operation. If desired, the independentactuated lead clamp 70 may include insulation or cushioning 76 on theend thereof. The independent actuated lead clamp 70 is actuatedindependently of bonding apparatus 26 and has the capability ofindependent movement along the x-axis, y-axis and z-axis with respect tothe bonding apparatus 26. The independent actuated lead clamp 70 is alsofree to move about the bonding apparatus 26 and the central axis of thedie 10 so that any lead finger 14 of a conventional lead frame that isto be connected to bond pads on the die 10, regardless of location, maybe accommodated. The independent actuated lead clamp 70 does not need tobe, and preferably is not, concentrically centered about the bondingapparatus 26 so that it will not interfere with the operation thereof.Any desired number of independent actuated lead clamps 70 may be usedabout the bonding apparatus to minimize the amount of movement of theindependent actuated lead clamp 70 between wire bonding operations. Theindependent actuated lead clamp 70 may be located in quadrants about thedie 10 in any manner as desired.

[0072] During the bond operation, one or more of the independentactuated lead clamps 70 clamps the end 15 of lead finger 14 of aconventional lead frame prior to the bonding of a wire 16 thereto by oneor more of the bonding apparatus 26. The independent actuated lead clamp70 applies sufficient pressure to the end 15 of lead finger 14 to pressthe lead finger 14 against movable and/or adjustable arm 24 to insure asatisfactory bond between the end 18 of any wire 16 and the end 15 ofthe lead finger 14.

[0073] As shown, one or more of the independent actuated lead clamps 70contacts the end 15 of lead finger 14 aft of the area of the bond ofwire end 18 to the lead finger 14. The bonds of the wire end 18 to theend 15 of the lead finger 14 are typically a wedge type wire bond,although a ball bond may be made if desired. As shown, the heat block 20is in contact with the paddle 12 and the movable and/or adjustable arm24, which, in turn, is in contact with the lead fingers 14.

[0074] The independent actuated lead clamp 70 may have a modified end orfoot thereon to provide a larger clamping area of the independentactuated lead clamp 70 on the end 15 of the lead finger 14 duringbonding operations. The modified end or foot may be substantially thesame width as the lead finger 14 of a conventional lead frame and may bemounted to have articulated movement about the end of the independentactuated lead clamp 70, such as using a pin extending through suitableapertures in a pair of ears attached to the foot.

[0075] The independent actuated lead clamp 70 may be integrally attachedto the conventional clamp 22 or may have an articulated mountingarrangement. The modified end or foot may be generally semicircular orarcuate in configuration so as to engage a large portion of the end 15of the lead finger 14 of a conventional lead frame surrounding thebonding apparatus 26 during the wire bonding operation to hold the end15 in position.

[0076] The independent actuated lead clamp 70 may also be used inconjunction with a second independently actuated clamp. The secondindependently actuated clamp may be of any suitable type and structuresuch as described and illustrated hereinbefore. The independent actuatedlead clamp 70 and the second clamp may be actuated independently of eachother and independently of the bonding apparatus 26 as described andillustrated hereinbefore.

[0077] Referring to drawing FIG. 8, an independently actuated lead clamp70 is shown having a lead finger penetrating portion 78 on the bottomthereof used in place of or in addition to the conventional clamp 22 tomaintain the lead finger 14 of a conventional lead frame during thebonding process. One or more of the independent actuated lead clamps 70having lead finger penetrating portions 78 located thereon contacts andpenetrates the end 15 of lead finger 14 aft of the area of the bond ofwire end 18 to the lead finger 14. The independent actuated lead clamp70 having lead finger penetrating portion 78 thereon may be of anysuitable shape for use in independently clamping the lead finger 14, inplace of the use of conventional clamp 22, such as square, semicircular,rectangular, arcuate, etc. Also, as shown, the independent actuated leadclamp 70 having lead finger penetrating portion 78 thereon may beresiliently mounted through the use of a shoulder 72 thereon abutting aspring 74 to control the amount of force exerted on any lead finger 14during the wire bonding operation. As described hereinbefore, theindependent actuated lead clamp 70 having lead finger penetratingportion 78 thereon is actuated independently of bonding apparatus 26 andhas the capability of independent movement along the x-axis, y-axis andz-axis with respect to the bonding apparatus 26. The independentactuated lead clamp 70 having lead finger penetrating portion 78 thereonis also free to move about the bonding apparatus 26 and the central axisof the die 10 so that any lead finger 14 of a conventional lead framethat is to be connected to a bond pad on the die 10, regardless oflocation, may be accommodated. The independent actuated lead clamp 70having lead finger penetrating portion 78 thereon does not need to be,and preferably is not, concentrically centered about the bondingapparatus 26 so that it will not interfere with the operation thereof.Any desired number of independent actuated lead clamps 70 having leadfinger penetrating portion 78 thereon may be used about the bondingapparatus to minimize the amount of movement of the independent actuatedlead clamp 70 between wire bonding operations. Also, the independentactuated lead clamps 70 may be located in quadrants about the die 10, orin any manner as desired.

[0078] The independently actuated lead clamp 70 has a lead fingerpenetrating portion 78 on the bottom thereof used in place of or inaddition to the conventional clamp 22 to maintain the lead finger 14 inposition during the bonding process. Such independent actuated leadclamp 70 helps insure that the lead finger 14 is in contact with themovable and/or adjustable arm 24 during the bonding process, immobilizesthe lead finger 14 during the wire bonding process, and helps minimizeany deflection of the end 15 of the lead finger 14 so that the bondingapparatus 26 accurately, precisely contacts the end 15 to provide thedesired wire bond. The action of such independent actuated lead clamp70, and, if desired the additional use of conventional clamp 22,provides improved clamping and immobilization of a lead finger 14 duringthe wire bonding process as well as insures that the lead finger 14 isin intimate contact with the movable and/or adjustable arm 24 foreffectiveness.

[0079] During the wire bonding process, it is desirable for the heatblock 20 to be heated as previously described hereinbefore. Similarly,the bonding apparatus 26 should exert substantially the same amount offorce as described hereinbefore.

[0080] During the bond operation, one or more of the independentactuated lead clamps 70 having a lead finger penetrating portion 78located on the end thereof clamps the end 15 of lead finger 14 prior tothe bonding of a wire 16 thereto by one or more of the bonding apparatus26. The independent actuated lead clamp 70 applies sufficient pressureto the end 15 of the lead finger 14 to insure a satisfactory bondbetween the end of any wire 16 and the end 15 of the lead finger 14.

[0081] As shown, one or more of the independent actuated lead clamps 70contacts the end 15 of lead finger 14 aft of the area of the bond ofwire end 18 to the lead finger 14. The bonds of the wire end 18 to theend 15 of the lead finger 14 are typically a wedge type wire bond,although a ball bond may be made if desired. As shown, the heat block 20is in contact with the paddle 12 of the lead frame. The lead fingers 14of a conventional lead frame are in contact with the movable and/oradjustable arm 24 which, in turn, is in contact with the heat block 20.

[0082] As also shown, the conventional clamps 22 are formed to have apenetrating portion 80 thereon which penetrates the end 15 of leadfinger 14 of a conventional lead frame. In this manner, the conventionalclamp 22 provides improved clamping and immobilization of a lead finger14 during the wire bonding process as well as insures that the leadfinger 14 is in intimate contact with the movable and/or adjustable arm24 for effectiveness. As shown, the clamps 22 and 70 having lead fingerpenetrating portions thereon cause the lead finger 14 to engage themovable and/or adjustable arm 24 with the movable and/or adjustable armbeing in contact with the heat block 20. However, care should be takento prevent the lead finger penetrating portion 78 of the independentactuated lead clamp 70 from either damaging the lead finger 14,affecting its electrical characteristics, or severing the lead finger14.

[0083] The independent actuated lead clamp 70 may be formed having amodified end or foot thereon to provide a larger clamping area of theindependent actuated lead clamp 70 on the end 15 of the lead finger 14during bonding operations. The modified end or foot is substantially thesame width as the lead finger 14 and may be mounted to have articulatedmovement about the end of the independent actuated lead clamp 70, suchas using a pin extending through suitable apertures in a pair of earsattached to the foot and the end of the modified independent actuatedlead clamp 70. Located on the bottom of the modified end or foot of theindependent actuated lead clamp 70 are suitable lead finger penetratingmembers which penetrate the lead finger 14 to immobilized it during wirebonding operations as described hereinbefore. The lead fingerpenetrating portion 78 may comprise a plurality of round shaped memberslocated to either extend along the axis of a lead finger 14 or extendtransversely thereof or may comprise a knife edge shape extendingtransversely across the axis of a lead finger 14. The shapes are to bemerely illustrative of a variety of shapes for the lead fingerpenetrating portion 78 which may be used. The modified end or foot maybe semicircular or arcuate in configuration so as to engage a largeportion of the end 15 of the lead finger 14 surrounding the bondingapparatus 26 during the wire bonding operation to hold the end 15 inposition. Also, a soft metal coating located on the lead finger 14 maybe penetrated by either the independent actuated lead clamp 70 or theconventional clamp 22. The soft metal coating applied to the lead finger14 may be of any suitable type, such as gold, silver, aluminum, etc.,which will allow for the easy penetration of the coating by a portion ofeither the independent actuated lead clamp 70 or the conventional clamp22. The independent actuated lead clamp 70 may act on the opposite sideof the lead from the bonding apparatus 26. It should be understood thatany of the penetrating clamps hereinbefore described may act on theopposite side of the conventional clamp 22 during the wire bondingoperations regarding a lead finger 14. It is not necessary that thepenetrating clamp be positioned on the same side of the lead finger 14as the bonding apparatus 26.

[0084] Referring to drawing FIG. 9, a semiconductor device (die) 10 isshown in relation to a leads-over-chip (LOC) lead frame without beingsupported directly by adhesive connection to the lead fingers 14 of thelead frame. (Note, that as shown in FIGS. 9 through 14, the die 10 issupported only by the wire 16 between the bond pads on the die 10 andthe lead fingers 14.) A heat block 20 is used to heat the die 10 duringthe wire bonding process. As shown, a suitable wire 16, as describedhereinbefore, has one end thereof 17 bonded to a bond pad of the die 10.The wire 16 may be of any suitable type for connection and bondingpurposes, such as gold, gold alloy, aluminum, aluminum alloy, etc. Theother end 18 of the wire 16 is shown being bonded to the end 15 of alead finger 14 of the lead frame by a suitable bonding apparatus 26. Thebonding apparatus 26 may be of any suitable type well known in thebonding area, such as described hereinbefore. If desired, in the wirebonding operation, further shown in contact with lead finger 14 is aportion of a conventional clamp 22 used to clamp portions of the leadframe during such bonding operations. The conventional clamp 22 may beof any well known suitable type, such as those described hereinbefore,and is generic in shape. Further shown in drawing FIG. 9 is movableand/or adjustable arm 24 having a lead support portion 25 attached to oran integral part of the movable and/or adjustable arm 24. The movableand/or adjustable arm 24 is dynamically attached to the heat block 20 sothat the lead support portion 25 can be positioned between the die 10and the lead fingers 14 of the LOC lead frame. The movable and/oradjustable arm 24 and lead support portion 25 thus substantially preventthe application of any force against the die 10 from the bondingapparatus 26 and the conventional clamp 22. In addition, movable and/oradjustable arm 24 and lead support portion 25 conduct heat from the heatblock 20 to the lead fingers 14. The action of movable and/or adjustablearm 24 and lead support portion 25 provide improved support of a leadfinger 14 during the wire bonding process, as well as insure that theforce applied by bonding apparatus 26 and conventional clamp 22 issubstantially against lead support portion 25 and movable and/oradjustable arm 24 rather than against the die 10. After the bonding ofthe wire 16 to the lead fingers 14 of the LOC lead frame, the wires 16support the die 10 during subsequent molding operations to encapsulatethe die 10 and a portion of the LOC lead frame.

[0085] The movement of the movable and/or adjustable arm 24 may beeffectuated by various means 28, such as described hereinbefore.

[0086] The movable and/or adjustable arm 24 is dynamically attached tothe heat block 20 so that as the heat block moves into position duringthe wire bonding process. The movable and/or adjustable arm and leadsupport portion 25 move into position between the lead fingers 14 andthe die 10. As shown, movable and/or adjustable arm 24 is shown astraveling against the heat block 20 such that the direction of travel issubstantially parallel with respect to the lower surface 19 of the leadfingers 14 of a LOC lead frame.

[0087] Referring to drawing FIG. 10, movable and/or adjustable arm 24may be attached to heat block 20 such that the direction of travel withrespect to lower surface 19 of lead fingers 14 of a LOC lead frame isangular or arcuate. A radius 54 may be formed in heat block 20 andmovable and/or adjustable arm 24 such that the direction of travel oflead support portion 25 and movable and/or adjustable arm 24 is arcuatewith respect to lower surface 19 of the lead fingers 14 of aconventional lead frame as the lead support portion is positioned priorto wire bonding.

[0088] Referring to drawing FIG. 11, the surface of the heat block 20and movable and/or adjustable arm 24 may also be angled 56 with respectto lower surface 19 of the lead fingers 14 of a LOC lead frame such thatthe direction of travel of lead support portion 25 and movable and/oradjustable arm 24 is angular with respect to lower surface 19 of leadfingers 14 of a LOC lead frame as the lead support portion and movablearm are positioned prior to the wire bonding process.

[0089] The movement of the movable and/or adjustable arm 24 and the heatblock 20 may be integrated so that as the heat block moves into positionit causes the movable arm to move into position. As shown, notch 50 isformed in movable and/or adjustable arm 24 and extends into a slot 52formed in a stationary member (not shown). Thus, as the heat block 20moves upward to contact the die 10, the heat block pushes against themovable and/or adjustable arm 24 which is forced to travel upward andinward by the notch 50 traveling in the slot 52.

[0090] Referring to drawing FIG. 12, a dual clamp assembly is shown inconjunction with the movable and/or adjustable arms 24 in order tofurther stabilize the lead fingers 14 of a LOC lead frame during thewire bonding process. The conventional clamp 22 acts as a primary clampand includes a bond site window 60. The bond site window 60 is sized toallow access for a bonding apparatus 26 to a plurality of bond pads ofsemiconductor die 10 and to a plurality of lead fingers 14 of aconventional lead frame.

[0091] The bond site window 60 includes a secondary clamp 62. Thesecondary clamp 62 has the same construction and operation as has beendescribed hereinbefore.

[0092] The semiconductor die 10 has a LOC lead frame arrangement whereinthe lead fingers 14 extend over the upper (active) semiconductor die 10.The bond site window contact lip 65 contacts the lead fingers 14 of theLOC lead frame around the periphery of the semiconductor die 10. Thesecondary clamp 62 extends toward the center of the semiconductor die10. A plurality of wires 16 is then attached between the bond pads ofthe semiconductor die 10 and the lead fingers 14.

[0093] The contact end 63 of the secondary clamp 62 in its unbiasedstate preferably extends slightly below a bond site window contact lip65 of the bond site window 60 of the clamp 22.

[0094] Referring to drawing FIG. 13, an independently actuated leadclamp 70 is shown in conjunction with the movable and/or adjustable arms24 in order to further stabilize the lead fingers 14 of a LOC lead frameduring the wire bonding process. Independently actuated lead clamp 70may be used in place of or in addition to the conventional clamp 22 tomaintain the lead finger 14 in position during the bonding process. Theconventional clamp 22 is the same as hereinbefore described inconstruction and operation to help insure that the lead finger is incontact with the movable and/or adjustable arm 24 during the bondingprocess and helps minimize any deflection of the end 15 of the leadfinger 14 so that the bonding apparatus 26 accurately and preciselycontacts the end 15 to provide the desired wire bond. The action ofindependent actuated lead clamp 70 and, if desired, the additional useof conventional clamp 22, provides improved clamping of a lead finger 14during the wire bonding process as well as insures that the lead finger14 of a conventional lead frame is in intimate contact with the movableand/or adjustable arm 24 for effectiveness.

[0095] Referring to drawing FIG. 14, as described hereinbefore, anindependently actuated lead clamp 70 is shown having a lead fingerpenetrating portion 78 on the bottom thereof used in place of or inaddition to the conventional clamp 22 to maintain the lead finger 14 ofa LOC lead frame during the bonding process. One or more of theindependent actuated lead clamp 70 having penetrating lead fingerportions 78 located thereon contacts and penetrates the end 15 of leadfinger 14 aft of the area of the bond of wire end 18 to the lead finger14.

[0096] Referring to drawing FIG. 15, a semiconductor device (die) 10 isshown in relation to a leads-over-chip (LOC) lead frame being supporteddirectly by adhesive attachment through adhesive coatings 1 on the tape2 to the lead fingers 14 on the lead frame. (Also, note that as shown inFIGS. 15 through 20 a die 10 is shown in relation to a LOC lead framebeing supported directly by adhesive attachment through adhesivecoatings 1 on the tape 2 to the lead fingers 14 on the lead frame.) Aheat block 20 is used to heat the die 10 during the wire bondingprocess. As shown, a suitable wire 16, as described hereinbefore, hasone end thereof 17 bonded to a bond pad of the die 10. The other end 18of the wire 16 is shown being bonded to the end 15 of a lead finger 14of the lead frame by a suitable bonding apparatus 26. The bondingapparatus 26 may be of any suitable type well known in the bonding areaas described hereinbefore. If desired, in the wire bonding operation,further shown in contact with lead finger 14 is a portion of aconventional clamp 22 used to clamp portions of the lead frame duringsuch bonding operations. The conventional clamp 22 may be of any wellknown suitable type, such as those described hereinbefore, and isgeneric in shape. Further shown in drawing FIG. 15 is movable and/oradjustable arm 24 having a lead support portion 25 attached to or anintegral part of the movable and/or adjustable arm 24. The movableand/or adjustable arm 24 is dynamically attached to the heat block 20 sothat the lead support portion 25 can be positioned between the die 10and the lead fingers 14 of the LOC lead frame. The movable and/oradjustable arm 24 and lead support portion 25 thus substantially preventthe application of any force against the die 10 from the bondingapparatus 26 and the conventional clamp 22. In addition, movable and/oradjustable arm 24 and lead support portion 25 conduct heat from the heatblock 20 to the lead fingers 14. The action of movable and/or adjustablearm 24 and lead support portion 25 provides improved support of a leadfinger 14 during the wire bonding process as well as insures that theforce applied by bonding apparatus 26 and conventional clamp 22 issubstantially against lead support portion 25 and movable and/oradjustable arm 24 rather than against the die 10. During subsequentmolding operations to encapsulate the die 10, a portion of the LOC leadframe of the die 10 is supported by the lead fingers 14 of the LOC leadframe through the adhesive coatings 1 and tape 2.

[0097] The movement of the movable and/or adjustable arm 24 may beeffectuated by various means 28 as described hereinbefore.

[0098] The movable and/or adjustable arm 24 is dynamically attached tothe heat block 20 so that as the heat block moves into position duringthe wire bonding process, the movable and/or adjustable arm 24 and leadsupport portion 25 move into position between the lead fingers 14 andthe die 10. The movable arm 24 is shown as traveling against the heatblock 20 such that the direction of travel is substantially parallelwith respect to the lower surface 19 of the lead fingers 14 of a LOClead frame.

[0099] Referring to drawing FIG. 17, movable and/or adjustable arm 24may be attached to heat block 20 such that the direction of travel withrespect to lower surface 19 of lead fingers 14 of a LOC lead frame isangular or arcuate. A radius 54 may be formed in heat block 20 andmovable and/or adjustable arm 24 such that the direction of travel oflead support portion 25 and movable and/or adjustable arm 24 is arcuatewith respect to lower surface 19 of the lead fingers 14 of aconventional lead frame as the lead support portion is positioned priorto wire bonding.

[0100] Referring to drawing FIG. 16, the surface of the heat block 20and movable and/or adjustable arm 24 may also be angled 56 with respectto lower surface 19 of the lead fingers 14 of a LOC lead frame such thatthe direction of travel of lead support portion 25 and movable and/oradjustable arm 24 is angular with respect to lower surface 19 of leadfingers 14 of a LOC lead frame as the lead support portion 25 andmovable and/or adjustable arm 24 are positioned prior to the wirebonding process.

[0101] The movement of the movable and/or adjustable arm 24 and the heatblock 20 may be integrated so that as the heat block moves into positionit causes the movable and/or adjustable arm to move into position. InFIG. 16, a notch 50 is shown formed in movable and/or adjustable arm 24and extends into a slot 52 formed in a stationary member (not shown).Thus, as the heat block 20 moves upward to contact the die 10, the heatblock pushes against the movable and/or adjustable arm 24 which isforced to travel upward and inward by the notch 50 traveling in the slot52.

[0102] Referring to drawing FIG. 18, a dual clamp assembly is shown inconjunction with the movable and/or adjustable arms in order to furtherstabilize the lead fingers 14 of a LOC lead frame during the wirebonding process. The conventional clamp 22 acts as a primary clamp andincludes a bond site window 60. The bond site window 60 is sized toallow access for a wire bonding apparatus 26 to a plurality of bond padsof semiconductor die 10 and to a plurality of lead fingers 14 of aconventional lead frame.

[0103] The bond site window 60 includes a secondary clamp 62. Thesecondary clamp 62 is mounted to a resilient plate 64 with a first setscrew or bolt 66. The proximal end of each resilient plate 64 isattached to the conventional clamp 22 with a second set screw or bolt68. It is, of course, understood that secondary clamp 62 can be attachedto the conventional clamp 22 in any number of known configurations,including forming the secondary clamp 62 with an integral resilientportion which is secured to the conventional clamp 22 or forming (forexample, as by machining) the secondary clamp 62 as an integrated,resilient appendage of the conventional clamp 22. It is, of course, alsounderstood that any number of secondary clamps 62 can be used,consistent with the need for adequate clearances for wire bonding.

[0104] As described hereinbefore, when a semiconductor die 10 and a leadframe strip including lead fingers 14 of a LOC lead frame are alignedwith the bond site window 60 in the conventional clamp 22 and pressureis exerted on the lead frame, the contact end 63 of the secondary clamp62 contacts the movable and/or adjustable arm 24 through lead fingers 14extending from the lead frame over the active die surface. The secondaryclamp 62 does not damage the semiconductor die 10 under the secondaryclamp contact end 63 because of the resilient nature of the secondaryclamp 62 and because of movable and/or adjustable arm 24 positionedbetween the semiconductor die 10 and the secondary clamp 62. Thesemiconductor die 10 has a LOC lead frame arrangement wherein the leadfingers 14 extend over the upper (active) semiconductor die 10. The bondsite window contact lip 65 contacts the lead fingers 14 of the LOC leadframe around the periphery of the semiconductor die 10. The secondaryclamp 62 extends toward the center of the semiconductor die 10. Aplurality of wires 16 is then attached between the bond pads of thesemiconductor die 10 and the lead fingers 14.

[0105] The contact end 63 of the secondary clamp 62 in its unbiasedstate preferably extends slightly below a bond site window contact lip65 of the bond site window 60 of the conventional clamp 22. Thesecondary clamp 62 may be formed from a substantially rigid,non-deformable material such as metal, high-temperature plastic, fibercomposites, or the like. A preferred material for the secondary clamp 62is 440C stainless steel.

[0106] Referring to drawing FIG. 19, an independently actuated leadclamp 70 is shown in conjunction with the movable and/or adjustable arms24 in order to further stabilize the lead fingers 14 of a LOC lead frameduring the wire bonding process. Independently actuated lead clamp 70may be used in place of or in addition to the conventional clamp 22 tomaintain the lead finger 14 in position during the bonding process. Theconventional clamp 22 is the same as hereinbefore described in structureand operation to help insure that the lead finger is in contact with themovable and/or adjustable arm 24 during the bonding process and helpsminimize any deflection of the end 15 of the lead finger 14 so that thebonding apparatus 26 accurately and precisely contacts the end 15 toprovide the desired wire bond. The action of independent actuated leadclamp 70 and, if desired, the additional use of conventional clamp 22,provides improved clamping of a lead finger 14 during the wire bondingprocess as well as insures that the lead finger 14 of a conventionallead frame is in intimate contact with the movable and/or adjustable arm24 for effectiveness.

[0107] Referring to drawing FIG. 20, as described hereinbefore, anindependently actuated lead clamp 70 is shown having a lead fingerpenetrating portion 78 on the bottom thereof used in place of or inaddition to the conventional clamp 22 to maintain the lead finger 14 ofa LOC lead frame during the bonding process. One or more of theindependent actuated lead clamps 70 having lead finger penetratingportions 78 located thereon contacts and penetrates the end 15 of leadfinger 14 aft of the area of the bond of wire end 18 to the lead finger14. The independent actuated lead clamp 70 having lead fingerpenetrating portion 78 thereon may be of any suitable shape for use inindependently clamping the lead finger 14, in place of the use ofconventional clamp 22. Also, as shown, the independent actuated leadclamp 70 having lead finger penetrating portion 78 thereon may beresiliently mounted through the use of a shoulder 72 thereon abutting aspring 74 to control the amount of force exerted on any lead finger 14during the wire bonding operation.

[0108] Referring to drawing FIG. 21, a semiconductor device (die) 10 isshown being supported by the paddle 12 of a two piece lead frame, suchas described in U.S. Pat. No. 4,984,059. A heat block 20 is used to heatthe paddle 12 and die 10 during the wire bonding process. As shown, asuitable wire 16, such as described hereinbefore, has one end thereof 17bonded to a bond pad of the die 10. The other end 18 of the wire 16 isshown being bonded to the end 15 of a lead finger 14 of the lead frameby a suitable bonding apparatus 26. The bonding apparatus 26 may be ofany suitable type well known in the bonding area, such as describedhereinbefore. If desired, in the wire bonding operation, further shownin contact with lead finger 14 is a portion of a conventional clamp 22used to clamp portions of the lead frame during such bonding operations.The conventional clamp 22 may be of any well known suitable type, suchas those described hereinbefore, and is generic in shape. Further shownin drawing FIG. 21 is movable and/or adjustable arm 24 having a leadsupport portion 25 attached to or an integral part of the movable and/oradjustable arm 24. The movable and/or adjustable arm 24 is dynamicallyattached to the heat block 20 so that the lead support portion 25 can bepositioned between the die 10 and the lead fingers 14. The movableand/or adjustable arm 24 and lead support portion 25 thus substantiallyprevent the application of any force against the die 10 from the bondingapparatus 26 and the conventional clamp 22. In addition, movable and/oradjustable arm 24 and lead support portion 25 conduct heat from the heatblock 20 to the lead fingers 14. The action of movable and/or adjustablearm 24 and lead support portion 25 provides improved support of a leadfinger 14 during the wire bonding process as well as insures that theforce applied by bonding apparatus 26 and conventional clamp 22 issubstantially against lead support portion 25 and movable and/oradjustable arm 24 rather than against the die 10.

[0109] The movement of the movable and/or adjustable arm 24 may beeffectuated by various means 28, such as described hereinbefore.

[0110] The movable and/or adjustable arm 24 is dynamically attached tothe heat block 20 so that as the heat block moves into position duringthe wire bonding process, the movable and/or adjustable arm 24 and leadsupport portion 25 move into position between the lead fingers 14 andthe die 10. The movable and/or adjustable arm 24 is shown as travelingagainst the heat block 20 such that the direction of travel issubstantially parallel with respect to the lower surface 19 of the leadfingers 14 of a conventional lead frame.

[0111] Referring to drawing FIG. 22, movable and/or adjustable arm 24may be attached to heat block 20 such that the direction of travel withrespect to lower surface 19 of lead fingers 14 is angular or arcuate. Aradius 54 may be formed in heat block 20 and movable and/or adjustablearm 24 such that the direction of travel of lead support portion 25 andmovable and/or adjustable arm 24 is arcuate with respect to lowersurface 19 of the lead fingers 14 of a conventional lead frame as thelead support portion 25 is positioned prior to wire bonding.

[0112] Referring to drawing FIG. 23, the surface of the heat block 20and movable and/or adjustable arm 24 may also be angled 56 with respectto lower surface 19 of the lead fingers 14 such that the direction oftravel of lead support portion 25 and movable and/or adjustable arm 24is angular with respect to lower surface 19 of lead fingers 14 as thelead support portion 25 and movable and/or adjustable arm 24 arepositioned prior to the wire bonding process.

[0113] The movement of the movable and/or adjustable arm 24 and the heatblock 20 may be integrated so that as the heat block moves into positionit causes the movable and/or adjustable arm to move into position. InFIG. 23, a notch 50 is shown formed in movable and/or adjustable arm 24and extends into a slot 52 formed in a stationary member (not shown).Thus, as the heat block 20 moves upward to contact the die 10, the heatblock pushes against the movable and/or adjustable arm 24 which isforced to travel upward and inward by the notch 50 traveling in the slot52.

[0114] Referring to drawing FIG. 24, a dual clamp assembly is shown inconjunction with the movable and/or adjustable arms 24 in order tofurther stabilize the lead fingers during the wire bonding process. Theconventional clamp 22 acts as a primary clamp and includes a bond sitewindow 60. The bond site window 60 is sized to allow access for abonding apparatus 26 to a plurality of bond pads of semiconductor die 10and to a plurality of lead fingers 14 of a conventional lead frame.

[0115] The bond site window 60 includes a secondary clamp 62 the same inconstruction and operation as described hereinbefore. The secondaryclamp 62 is mounted to a resilient plate 64 with a first set screw orbolt 66. The proximal end of each resilient plate 64 is attached to theconventional clamp 22 with a second set screw or bolt 68. It is, ofcourse, understood that secondary clamp 62 can be attached to theconventional clamp 22 in any number of known configurations, includingforming the secondary clamp 62 with an integral resilient portion whichis secured to the conventional clamp 22 or forming (for example, as bymachining) the secondary clamp 62 as an integrated, resilient appendageof the conventional clamp 22. It is, of course, also understood that anynumber of secondary clamps 62 can be used, consistent with the need foradequate clearances for wire bonding.

[0116] When a semiconductor die 10 and a lead frame strip including leadfingers 14 of a two piece lead frame is aligned with the bond sitewindow 60 in the conventional clamp 22 and pressure is exerted on thelead frame, the contact end 63 of the secondary clamp 62 contacts themovable and/or adjustable arm 24 through lead fingers 14 extending fromthe lead frame over the active die surface. The secondary clamp 62 doesnot damage the semiconductor die 10 under the secondary clamp contactend 63 because of the resilient nature of the secondary clamp 62 andbecause of movable and/or adjustable arm 24 positioned between thesemiconductor die 10 and the secondary clamp 62.

[0117] The semiconductor die 10 has a two piece lead frame arrangementwherein the lead fingers 14 extend over the upper (active) semiconductordie 10. The bond site window contact lip 65 contacts the lead fingers 14around the periphery of the semiconductor die 10. The secondary clamp 62extends toward the center of the semiconductor die 10. A plurality ofwires 16 is then attached between the bond pads of the semiconductor die10 and the lead fingers 14.

[0118] The contact end 63 of the secondary clamp 62 in its unbiasedstate preferably extends slightly below bond site window contact lip 65of the bond site window 60 of the conventional clamp 22.

[0119] Referring to drawing FIG. 25, an independently actuated leadclamp 70, such as described hereinbefore, is shown in conjunction withthe movable and/or adjustable arms 24 in order to further stabilize thelead fingers 14 of a two piece lead frame during the wire bondingprocess. Independently actuated lead clamp 70 may be used in place of orin addition to the conventional clamp 22 to maintain the lead finger 14in position during the bonding process. The conventional clamp 22 helpsinsure that the lead finger is in contact with the movable and/oradjustable arm 24 during the bonding process and helps minimize anydeflection of the end 15 of the lead finger 14 so that the bondingapparatus 26 accurately and precisely contacts the end 15 to provide thedesired wire bond. The action of independent actuated lead clamp 70 and,if desired, the additional use of conventional clamp 22, providesimproved clamping of a lead finger 14 during the wire bonding process aswell as insures that the lead finger 14 of a two piece lead frame is inintimate contact with the movable and/or adjustable arm 24 foreffectiveness.

[0120] Independent actuated lead clamp 70 may be of any suitable shapefor use in independently clamping the lead finger 14, in place of theuse of conventional clamp 22. Also, the independent actuated lead clamp70 may be resiliently mounted through the use of a shoulder 72 thereonabutting a spring 74 to control the amount of force exerted on any leadfinger 14 during the wire bonding operation. If desired, the independentactuated lead clamp 70 may include insulation or cushioning 76 on theend thereof.

[0121] During the bond operation, one or more of the independentactuated lead clamps 70 clamps the end 15 of lead finger 14 of a twopiece lead frame prior to the bonding of a wire 16 thereto by one ormore of the bonding apparatus 26. The independent actuated lead clamp 70applies sufficient pressure to the end 15 of lead finger 14 to press thelead finger 14 against movable and/or adjustable arm 24 to insure asatisfactory bond between the end 18 of any wire 16 and the end 15 ofthe lead finger 14.

[0122] As shown, one or more of the independent actuated lead clamps 70contacts the end 15 of lead finger 14 aft of the area of the bond ofwire end lead finger 14. The bonds of the wire end 18 to the end 15 ofthe lead finger 14 are typically a wedge type wire bond, although a ballbond may be made if desired. As shown, the heat block 20 is in contactwith the paddle 12 and the movable and/or adjustable arm 24, which, inturn, is in contact with the lead fingers 14.

[0123] The independent actuated lead clamp 70 may have a modified end orfoot thereon to provide a larger clamping area of the independentactuated lead clamp 70 on the end 15 of the lead finger 14 duringbonding operations. The modified end or foot may be substantially thesame width as the lead finger 14 of a conventional lead frame and may bemounted to have articulated movement about the end of the independentactuated lead clamp 70, such as using a pin extending through suitableapertures in a pair of ears attached to the foot.

[0124] The independent actuated lead clamp 70 may be integrally attachedto the conventional clamp 22 or may have an articulated mountingarrangement. The modified end or foot may be generally semicircular, orarcuate, in configuration so as to engage a large portion of the end 15of the lead finger 14 of a conventional lead frame surrounding thebonding apparatus 26 during the wire bonding operation to hold the end15 in position.

[0125] The independent actuated lead clamp 70 may also be used inconjunction with a second independently actuated clamp. The secondindependently actuated clamp may be of any suitable type and structuresuch as described and illustrated hereinbefore. The independent actuatedlead clamp 70 and the second clamp may be actuated independently of eachother and independently of the bonding apparatus 26 as described andillustrated hereinbefore.

[0126] Referring to drawing FIG. 26, an independently actuated leadclamp 70, such as described hereinbefore, is shown having a lead fingerpenetrating portion 78 on the bottom thereof used in place of or inaddition to the conventional clamp 22 to maintain the lead finger 14 ofa two-piece lead frame during the bonding process. One or more of theindependent actuated lead clamps 70 having lead finger penetratingportions 78 located thereon contacts and penetrates the end 15 of leadfinger 14 aft of the area of the bond of wire end 18 bonded to the leadfinger 14. The independent actuated lead clamp 70 having lead fingerpenetrating portion 78 thereon may be of any suitable shape for use inindependently clamping the lead finger 14, in place of the use ofconventional clamp 22. Also, as shown, the independent actuated leadclamp 70 having lead finger penetrating portion 78 thereon may beresiliently mounted through the use of a shoulder 72 thereon abutting aspring 74 to control the amount of force exerted on any lead finger 14during the wire bonding operation. As described hereinbefore, theindependent actuated lead clamp 70 having lead finger penetratingportion 78 thereon is actuated independently of bonding apparatus 26 andhas the capability of independent movement along the x-axis, y-axis andz-axis with respect to the bonding apparatus 26. The independentactuated lead clamp 70 having lead finger penetrating portion 78 thereonis also free to move about the bonding apparatus 26 and the central axisof the die 10 so that any lead finger 14 of a conventional lead framethat is to be connected to a bond pad on the die 10, regardless oflocation, may be accommodated. The independent actuated lead clamp 70having lead finger penetrating portion 78 thereon does not need to be,and preferably is not, concentrically centered about the bondingapparatus 26 so that it will not interfere with the operation thereof.Any desired number of independent actuated lead clamps 70 having leadfinger penetrating portion 78 thereon may be used about the bondingapparatus 26 to minimize the amount of movement of the independentactuated lead clamp 70 between wire bonding operations. Also, theindependent actuated lead clamps 70 may be located in quadrants aboutthe die 10, or in any manner as desired.

[0127] The independently actuated lead clamp 70 has a lead fingerpenetrating portion 78 on the bottom thereof used in place of or inaddition to the conventional clamp 22 to maintain the lead finger 14 inposition during the bonding process. Such independent actuated leadclamp 70 helps insure that the lead finger 14 is in contact with themovable arm 24 during the bonding process, immobilizes the lead finger14 during the wire bonding process, and helps minimize any deflection ofthe end 15 of the lead finger 14 so that the bonding apparatus 26accurately, precisely contacts the end 15 to provide the desired wirebond. The action of such independent actuated lead clamp 70 and, ifdesired, the additional use of conventional clamp 22, provides improvedclamping and immobilization of a lead finger 14 during the wire bondingprocess as well as insures that the lead finger 14 is in intimatecontact with the movable and/or adjustable arm 24 for effectiveness.

[0128] During the wire bonding process, it is desirable for the heatblock 20 to be heated as previously described hereinbefore. Similarly,the bonding apparatus 26 should exert substantially the same amount offorce as described hereinbefore.

[0129] During the bond operation, one or more of the independentactuated lead clamps 70 having a lead finger penetrating portion 78located on the end thereof clamps the end 15 of lead finger 14 prior tothe bonding of a wire 16 thereto by one or more of the bonding apparatus26. The independent actuated lead clamp 70 applies sufficient pressureto the end 15 of the lead finger 14 to insure a satisfactory bondbetween the end of any wire 16 and the end 15 of the lead finger 14.

[0130] As shown, one or more of the independent actuated lead clamps 70contacts the end 15 of lead finger 14 aft of the area of the bond ofwire end 18 bonded to the lead finger 14. The bonds of the wire end 18to the end 15 of the lead finger 14 are typically a wedge type wirebond, although a ball bond may be made if desired. As shown, the heatblock 20 is in contact with the paddle 12 of the lead frame. The leadfingers 14 of a two piece lead frame are in contact with the movableand/or adjustable arm 24 which, in turn, is in contact with the heatblock 20.

[0131] As also shown, the conventional clamps 22 are formed to have apenetrating portion 80 thereon which penetrates the end 15 of leadfinger 14 of a conventional lead frame. In this manner, the conventionalclamp 22 provides improved clamping and immobilization of a lead finger14 during the wire bonding process as well as insures that the leadfinger 14 is in intimate contact with the movable and/or adjustable arm24 for effectiveness. As shown, the clamps 22 and 70 having lead fingerpenetrating portions 78 thereon cause the lead finger 14 to engage themovable and/or adjustable arm 24 with the movable and/or adjustable armbeing in contact with the heat block 20. However, care should be takento prevent the lead finger penetrating portion 78 of the independentactuated lead clamp 70 from either damaging the lead finger 14,affecting its electrical characteristics, or severing the lead finger14.

[0132] The independent actuated lead clamp 70 may be formed having amodified end or foot thereon to provide a larger clamping area of theindependent actuated lead clamp 70 on the end 15 of the lead finger 14during bonding operations as described hereinbefore. It should beunderstood that any of the penetrating clamps hereinbefore described mayact on the opposite side of the conventional clamp 22 during the wirebonding operations regarding a lead finger 14. It is not necessary thatthe penetrating clamp be positioned on the same side of the lead finger14 as the bonding apparatus 26.

[0133] Referring to drawing FIG. 27, a semiconductor device (die) 10 isshown being supported by the paddle 12 of a hybrid lead frame havinglead fingers 14 located on differing levels with respect to thesemiconductor device 10. That is, a portion of the lead fingers islocated on a first level with respect to the lead frame and anotherportion of the lead fingers is located on a second level with respect tothe lead frame. The portion of the lead fingers 14 of the lead frame aresupported by heat block 20 during the bonding operation while the otherportion of lead fingers 14 is supported by the lead support portion 25of movable and/or adjustable arm 24 (not shown) during the wire bondingoperations. A heat block 20 is used to heat the paddle 12 and die 10during the wire bonding process. As shown, a suitable wire 16, such asdescribed hereinbefore, has one end thereof 17 bonded to a bond pad ofthe die 10. The wire 16 may be of any suitable type for connection andbonding purposes as described hereinbefore. The other end 18 of the wire16 is shown being bonded to the end 15 of a lead finger 14 of the leadframe by a suitable bonding apparatus 26. The bonding apparatus 26 maybe of any suitable type well known in the bonding area as describedhereinbefore. If desired, in the wire bonding operation, further shownin contact with lead finger 14 is a portion of a conventional clamp 22used to clamp portions of the lead frame during such bonding operations.The conventional clamp 22 may be of any well known suitable type, suchas those described hereinbefore, and is generic in shape. As shown indrawing FIG. 28, movable and/or adjustable arm 24 having a lead supportportion 25 is attached to or an integral part thereof. The movableand/or adjustable arm 24 is dynamically attached to the heat block 20 sothat the lead support portion 25 can be positioned under a portion ofthe lead fingers 14. The movable and/or adjustable arm 24 and leadsupport portion 25 thus allow for improved wire bonding to the elevatedlead fingers 14 of the hybrid lead frame. In addition, movable and/oradjustable arm 24 having lead support portion 25 conducts heat from theheat block 20 to the lead fingers 14.

[0134] The movement of the movable and/or adjustable arm 24 may beeffectuated by various means 28, such as described hereinbefore. Themovable and/or adjustable arm 24 is dynamically attached to the heatblock 20 so that as the heat block moves into position during the wirebonding process, the movable and/or adjustable arm 24 having leadsupport portion 25 moves into position under a portion of the leadfingers 14.

[0135] Referring to drawing FIG. 28, the movable and/or adjustable arm24 is shown in relation to the semiconductor device 10 and lead fingers14 of the hybrid lead frame. As illustrated, the heat block 20 supportsthe lower level or first portion of lead fingers 14 during wire bondingoperations while the lead support portion 25 of the movable and/oradjustable arm 24 supports the upper level or other portion of the leadfingers 14 during wire bonding operations by bonding apparatus 26.

METHOD OF BONDING

[0136] Referring to drawing FIGS. 1, 4 and 5, in the method of thepresent invention, a die 10 is positioned within the bonding area of thebonding apparatus 26. A movable and/or adjustable arm 24 having a leadsupport portion 25 is positioned such that the lead support portion 25is between the die 10 and the lead fingers 14. A conventional clamp 22serves to help straighten the lead frame and position the lead fingers14 during subsequent bonding operations. Next, the die 10 and the leadfingers 14 are heated to the desired temperature before bondingoperations by the heat block 20 acting through movable and/or adjustablearm 24. The wire bonding apparatus 26 is then actuated to form a wirebond on end 17 of wire 16 to an appropriate bond pad on die 10. Afterthe formation of the bond of end 17 of wire 16 to the bond pad of die10, the bonding apparatus is moved to appropriate end 15 of lead finger14 for the formation of a suitable wire bond thereto by end 18 of wire16. During this process, lead support portion 25 of movable and/oradjustable arm 24 acts to substantially oppose the application of forcefrom the bonding apparatus 26 and conventional clamp 22 and to stabilizethe lead fingers 14. After the wire 16 has been bonded to the desiredbond pad of die 10 and end 15 of lead finger 14, the process is repeateduntil all desired wire bonds between lead fingers 14 and bond pads ofdie 10 are completed.

[0137] Referring to drawing FIG. 6, if desired to have additionalclamping of the lead finger 14, a secondary clamp 62 and a conventionalclamp 22 may be used with the bonding apparatus 26. The secondary clamp62 may be actuated and moved from the lead finger 14 with, before orafter the removal of the bonding apparatus 26 from the lead finger.

[0138] Referring to drawing FIG. 7, if desired to have additionalclamping of the lead finger 14, either a conventional clamp 22 and/or asecond independent actuated lead clamp 70 may be used with the bondingapparatus 26. The second independent actuated lead clamp 70 may beactuated and moved from the lead finger 14 with, before or after theremoval of the bonding apparatus 26 from the lead finger.

[0139] Referring to drawing FIG. 8, if desired to have additionalclamping of the lead finger 14, either a conventional clamp 22 and/or asecond independent actuated lead clamp 70 having a lead fingerpenetrating portion 78 thereon may be used with the bonding apparatus26. The second independent actuated lead clamp 70 may be actuated andmoved from the lead finger 14 with, before or after the removal of thebonding apparatus 26 from the lead finger. It will be understood thatthe alternative embodiments of the present invention shown in the otherdrawing figures corresponding to those described hereinabove are wirebonded in a similar fashion.

[0140]FIG. 29 is a flow chart of a typical process sequence for plasticpackage molding of a semiconductor device wirebond to a lead frame bythe use of a lead support portion 25 of movable and/or adjustable arm 24according to the present invention. It should be noted that the solderdip/plate operation has been shown as one step for brevity; normallyplating would occur prior to trim and form.

[0141]FIGS. 30 and 31 show pre-molding and post-molding positions ofencapsulant during a transfer molding operation using a typical moldapparatus comprising upper and lower mold halves 500 and 502, each moldhalf including a platen 514 or 516 with its associated chase 518 or 520.Heating elements 522 are employed in the platens to maintain an elevatedand relatively uniform temperature in the runners and mold cavitiesduring the molding operation. FIG. 30 shows a top view of one side ofthe transfer mold apparatus of FIGS. 28 and 29. In the transfer moldapparatus shown, the encapsulant flows into each mold cavity 544 throughthe short end thereof.

[0142] In operation, a heated pellet of resin mold compound 530 isdisposed beneath ram or plunger 532 in pot 534. The plunger descends,melting the pellet and forcing the melted encapsulant down through sprue536 and into primary runner 538, from which it travels totransversely-oriented secondary runners 540 and across gates 542 intoand through the mold cavities 544 through the short side thereof flowingacross the die assemblies 100, wherein die assemblies 100 comprisingdies 102 with attached lead frames 104 are disposed (usually in stripsso that a strip of six lead frames, for example, would be cut and placedin and across the six cavities 544 shown in FIG. 32). Air in the runners538 and 540 and mold cavities 544 is vented to the atmosphere throughvents 546 and 548. At the end of the molding operation, the encapsulantis “packed” by application of a higher pressure to eliminate voids andreduce non-uniformities of the encapsulant in the mold cavities 544.After molding, the encapsulated die assemblies are ejected from thecavities 544 by ejector pins 550, after which they are post-cured at anelevated temperature to complete cross-linking of the resin, followed byother operations as known in the art and set forth in FIG. 29 by way ofexample. It will be appreciated that other transfer molding apparatusconfigurations, as well as variations in the details of the describedmethod are known in the art. However, none of such are pertinent to theinvention, and so will not be discussed herein.

[0143] Encapsulant flow in the mold cavities 544 is demonstrablynon-uniform. The presence of the die assembly 100 comprising a die 102with lead frame 104 disposed across the mid-section of a cavity 544splits the viscous encapsulant flow front 106 into upper 108 and lower110 components. Further, the presence of the (relatively) large die 102with its relatively lower temperature in the middle of a cavity 544permits the flow front 106 on each side of the die 102 to advance aheadof the front which passes over and under the die 102. FIGS. 33 and 34show two mold cavity encapsulant flow scenarios where, respectively, thelower flow front 110 and the upper flow front 108 lead the overallencapsulant flow front 106 in the cavity 544 containing the die assembly100. FIG. 35 depicts the advance of a flow front 106 from above, beforeand after a die 102 is encountered, the flow being depicted astime-separated instantaneous flow fronts 106 a, 106 b, 106 c, 106 d, 106e and 106 f.

[0144] It will be understood that the present invention may havechanges, additions, deletions, modifications, and a different sequenceof operation which fall within the scope of the invention. For instance,the lead support portion may be actuated in various directions withrespect to the semiconductor device during the wire bonding process. Thelead support portion may be segmented or in multiple pieces, etc.

What is claimed is:
 1. Apparatus for supporting at least one lead fingerof at least one lead frame for a wire bonding process connecting said atleast one lead finger to a semiconductor device comprising: at least onesupport for positioning below said at least one lead finger for saidwire bonding process, a surface of said at least one support forcontacting a bearing surface and for moving on a portion thereof, saidat least one support including a portion for positioning at a locationbetween said lead finger and said semiconductor device, the portion ofsaid at least one support contacting a lower surface of said at leastone lead finger located above the semiconductor device without providingsupport therefore; and a heating apparatus for heating at least saidsemiconductor device.
 2. The apparatus of claim 1, wherein said heatingapparatus includes a heating apparatus for heating said bearing surface.3. The apparatus of claim 1, wherein said at least one support includesa portion for supporting more than at least one lead finger.
 4. Theapparatus of claim 3, wherein said portion comprises a portion forpositioning adjacent a semiconductor device.
 5. The apparatus of claim3, wherein said portion comprises a portion for positioning adjacent asemiconductor device for exerting a force of a bonding apparatus tosubstantially apply the force against said portion.
 6. The apparatus ofclaim 3, wherein said portion comprises a portion for substantiallypreventing an application of force on a die by a bonding apparatus. 7.The apparatus of claim 3, wherein said portion comprises a portion forresisting a force of substantially 50 to 100 grams.
 8. The apparatus ofclaim 3, wherein said portion comprises a portion for positioningbetween said at least one lead finger and said semiconductor device. 9.The apparatus of claim 1, wherein said at least one support includes aplurality of portions for supporting more than an individual lead fingerof said lead frame.
 10. The apparatus of claim 1, further comprising anapparatus for moving said at least one support on said bearing surface.